In the field of home systems the IEEE 1394 bus has become an important communication system with asynchronous and isochronous transport capability. The IEEE 1394 serial bus already provides an internationally standardized and very widely accepted bus for data exchange between terminals from both, the consumer electronics field and the computer industry. The precise designation of the aforementioned standard is: IEEE Standard for high performance serial bus, (IEEE) STD 1394-1995, IEEE New York, August 1996. In 2000 an improved version has been finalised with the reference IEEE 1394-2000.
The IEEE 1394 bus is a wired bus and it is specified that a maximum of 63 stations can participate in the communication over the bus lines. The 63 stations can be distributed in a flat or house. The maximum distance between two stations is 4.5 m. However, there are also solutions existing that extend the distance.
A problem with all wired bus systems is that the bus cable needs to be installed in every room where a bus station shall be located. This problematic gave rise to the wish of a wireless extension of the IEEE 1394 standard. A standalone device or a cluster of devices shall communicate with a first cluster by means of a wireless link.
In the meantime there are wireless protocols existing that can be used for the wireless link. The document ‘Broadband Radio Access Networks (BRAN); Hiperlan Type 2; Packet based convergence layer; Part 3: IEEE 1394 Service Specific Convergence Sublayer (SSCS)” defines a sublayer emulating the IEEE 1394 link layer over a ETSI BRAN Hiperlan/2 wireless network. As such, it may be present in bridge devices between wired 1394 busses, or in standalone wireless devices. When two busses are connected through a bridge, these two busses are still considered distinctly from the point of view of the IEEE 1394 standard. Moreover, since the sublayer has to be present in a standalone device, standard 1394 devices first have to be modified in order to be linked to a network through a wireless link.
The interconnection of the different busses (with different bus_IDs) involves a IEEE 1394 bridge, which is currently under definition by the IEEE P1394.1 working group. Because of the use of different bus_IDs, an application operating on bridges shall be bridge aware.
The box that connects the 1394 bus cable of a cluster to the wireless bridge needs to have a standard conform interface but on the other hand it needs to have some additional functionality which concerns the self configuration phase of the network. The 1394 bus has live insertion capability and each time a device is added or removed from the bus a bus reset is performed. After a bus reset each bus node sends a self-id packet to the bus, with which all other stations on the bus become aware of how many stations are present on the bus. The ID-number is a 6 bit number so that 64 devices can be distinguished. There is a specific process defined in the 1394 standard with which the ID-numbers are assigned to the stations. This will be described in more detail later on.
If all the stations in the network shall be configured as belonging to one 1394 bus, the self-configuration phase must be performed in coordinated fashion in both clusters with the bridge circuit in-between.
The devices of the second cluster are not aware that they are connected via a wireless link to the network. To achieve transparent operation, it is necessary that the wireless converters shall generate Self-ID packets that are reflecting the topology on both busses.